Production of nitroalkanes and carbonyl compounds



oct. 29, 1 957 A. c. MoKlNNls PRODUCTION OF NITROALKANES AND CARBONYL COMPOUNDS Filed DBG. 10, 1954 /raadnwz /2 Aufn/f Milaan/m:

rum/mw United States Patent PRODUCTION OF NITROALKANES AND CARBONYL COMPOUNDS Art McKinnis, Long Beach, Calif., assigner, by mesne assignments, to Brea Chemicals, Inc., a corporation of California Application December 10, 1954, Serial No. 474,470

8 Claims. (Cl. 260-597) This invention relates to the nitration of olens with nitrogen tetroxide (N204) to produce predominantly addition products containing two atoms of nitrogen per molecule. It relates further to the hydrolytic treatment of the mixed addition products to produce ultimately a nitroalkane and either an aldehyde or ketone, depending upon the particular olefin employed. It has been found rstly that olens, particularly iso-olens, maybe nitrated with N204 under conditions which practically exclude the Patented Oct. 29, 1957 olen, and yields of aldehyde or ketone ranging between about 60*80%. These results are obtained moreover with relatively non-corrosive reactants, simple apparatus, and economical operating conditions, i. e. low temperatures and liquid phase.

It is therefore an object of the invention to provide a simple and economical method forf'producing nitromethane or other nitroalkanes, in high yields from inexpensive raw materials. Another object is to provide conditions for the liquid phase, low-temperature nitration of olelins ICC with N204 which will substantially eliminate side reactions v resulting in the formation of nitroso compounds, alkyl mono-nitrates, alkyl mono-nitrites and oxidation products, and will also concomitantly increase the yield of those nitrated products which may be hydrolyzed to form nitroalkanes and valuable carbonyl compounds. A further object is to provide hydrolysis conditions best adapted to convert the complex nitration mixture to a nitroalkane and a carbonyl compound, with a minimum of undesirable hydrolytic side-reactions. Other objects will appear hereinafter.

In the case of isobutene, the over-all reactions are apparently as follows:

l-a l-b (IH, CH2NO2 i H O 2 onse N204 onaoNo, -1k ornNo (Camco (Non' a H. CH3 E 1,2-dinitro Nitro- Acetone isobutane methane CHI CHzNO il g H CHsO N20; CHaCONO g CHaNOn -l- (CHshCO (N02) I a CH3 H3 i Nitrat-butyl Nitro- 'acetone nitrite methane CH, CHZNOz g ll O i H2O f CHaC N204 CHSCONOZ g i: CHQNO: (CHQMCO (NO3) l a n: CH3 l N itro-t-butyl Nitro- Aeetone nitrate methane formation of oxidation products, mono-nitrated products, and nitroso compounds, the product obtained consisting essentially of a mixture of nitro-nitrites, dinitro alkanes, and nitro-nitrates. Secondly it has been found that the mixture of nitro compounds may, Without intervening separation or purication, be subjected to hydrolysis and fission in the presence of water and mildly basic catalysts, under certain novel conditions which result ultimately in the substantially quantitative ission of each of the nitrated products to produce a mono-nitroalkane and either an aldehyde or a ketone.

The intermediate mixture of nitro compounds is useful as such, or it may be resolved into its components, which are useful as chemical intermediates, solvents, plasticizers, explosives, jet fuels and the like. The over-all process lhowever, is conceived as an economical route to vnitro- .methane and other nitroalkanes. Presently employed .methods for producing nitromethane require the high- 'temperature vapor-phase nitration of methane or other .alkane with nitric acid. This process is uneconomical l.from the standpoint of equipment costs, corrosion prob- ',lems, recovery and recycle of unreacted products, and the inherently low yields and conversions obtained. For example, with methane the maximum yields of nitromethane which have been obtained range between about 1Z0-25%, 'zbased on nitric acid. In the present case, the process -results in typical yields of nitromethane ranging between about 80-90% of theoretical, based on either N204 or It will be observed in each case that the nitrite and nitrate groups are added to the carbon atom containing the least number of hydrogen atoms, and this is the general case with other oleiins. Reaction 3-a takes place to a very small extent in the absence of added oxygen, and

0 more especially under the preferred reaction conditions wherein the contact time is limited to a few seconds.

The nitration step with N204 is preferably conducted in the presence of a suitable ether-type solvent. Suitable solvents include aliphatic, alicyclic, or aralkyl, ethers and esters, preferably those containing from 2 to 6 carbon atoms. Specific examples include dimethyl ether, diethyll ether, methylethyl ether, diisopropyl ether, methylal, dioxane, tetrahydrofuran, ethyl acetate, ethyl propionate, amyl acetate and the like. All of these solvents form addition complexes with N204, which complexes appear to be the actual nitrating agent. It is believed that the formation of such complexes may resolve the N204 into a single tautomeric form, thus inhibiting reaction of tautomeric forms such as 0N-ON02 with the olen.

The nitration is ordinarily carried out at -25 to +30 Y C., preferably between about -l0fand +15 C., and

preferably though not necessarily at atmospheric pressures. Temperatures above the maximum limits result in an undesirable increase in oxidation reactions, while lower temperatures unduly decrease the reaction rate. The nitration is carried out in the liquid phase, but in the case of the lower olens, ity may be desirable to .employ a the oxidizing eect of nitrous acid. In the high temperature hydrolytic fission step, the alkali, in addition to combining with the liberated nitrous acid, ialso appears to act as a catalyst for the hydrolytic iission of dinitro alkanes, nitro-nitrates, and nitro alcohols.

The choice of alkali employed in the hydrolysis steps may hinge upon the type of inorganic nitrite which is ultimately desired. While there is some preference for insoluble alkalies such as calcium carbonate, zinc oxide, magnesium oxide, aluminum hydroxide, etc., other stronger alkalies may be employed if care is exercised to avoid a large instantaneous excess thereof which would be available for combining with the nitro-alkanes. By observing this precaution, bases such as potassium hydroxide, sodium hydroxide, ammonium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, potassium carbonate, potassium bicarbonate, trisodium phosphate,` disodium phosphate, sodium acetate, sodium citrate and the like may also be employed. These materials may be added gradually in proportions sutlicient to maintain continuously during the hydrolysis reactions apH between about 4 and 10, preferably between about 5 and 9. In the case of the insoluble alkaline materials such as zinc oxide a stoichiometric excess may be employed and the desired pH range is automatically maintained.

The reactions which occur during hydrolysis and fission are not fully understood, but the more important reactions, as exemplified with the isobutene nitration 6 best understood by reference to the accompanying drawing which is a flowsheet illustrating a particular method for the nitration of isobutene to obtainultimately nitro-v methane and acetone. The isobutene, either in vapor 5 phase, liquid phase, or in solution, is admitted. to the nitration step 1 through line 2.V Liquid nitrogen tetroxide is brought in through line 3 and admixed with diethyl ether in line 4, both of which are then brought into the,

nitration step. The proportion of nitrogen tetroxide to` 10 ether may suitably, though not necessarily, range between about 0.5 and 5 moles of ether per mole of N204. The

proportion of isobutene may range e. g. between about 0.6 and 1.5 moles per mole of N204. In the interest of simplicity and to avoid the handling of excessive volumes, the three reactants admitted to the nitration step may be in roughly equal molar proportions, i. e. 1:l:l. The nitration is conducted as previously described, either batchwise in a suitable tank, or continuously in tubular reactor.

The temperature of nitration should be controlled as in- A dicated, preferably between about 10 and +15"Y C.

lf the nitration is conducted batch-wise, entaili'ng contact residence times in excess of about ten minutes, lit is essentialV that the reactants be substantially anhydrous. On the other hand if the reaction is continuous, and the contact time is limited to less than about 2 minutes, as much as 3-4% by volume of water may be tolerated in the nitration step.

The complete nitration mixture line 5 to the low temperature hydrolysis step indicated at 6,V wherein hydrolysis in the presence of water and an oHsNor termico (No.)-

products, are believed to be as follows:

CHzNOn A CHNO: A CHaNOz A Hz z Hz CH3 N01 CH3 T CH: OH

S. Ha H3 Hg CHzNO o CHzNOn A0 on. y#ONO i ouais-on oHaNo2+ (onmoo (No2)- v CH. Ha

CHiNOi A CHNO, A CHiNoi A Tiry H20 (IJ H10 f CHH- -oNOr T CHt T CHE-0H T CHaNot-l- (CHmoo (Noi)- B4 E a f He Hs Hz n It has not beentdetermined exactly which of the above individual reactions take place during the low temperature hydrolysis, and which take place during the high temperature iission. It does appear however that the initial hydrolysis of nitro-tert butyl nitrite in Equation Z-b occurs exclusively and vrapidly during the low temperaturehydrolysis, while the final fissionv of the intermediates to form nitromethane and acetone takes place predominantly or exclusively during the high temperature treatment. It has been observed moreover that lower yields of nitromethane are obtained when the nitration mixture is.

transferred directly to the boiling hydrolytic medium, without theL intervening low temperature hydrolysis. It would appear therefore that it is preferable to eliminate the organic nitrite groups prior to vthe high temperature ssion, probably avoiding thereby the oxidative elfects ofa sudden large excess of nitrous acid which would be liberated so rapidly at high temeratures as to cause serious oxidation before it is neutralized by the alkali. This seems especially likelywhere insoluble alkalis such as zinc oxidev are employed. It is also possible that the terminal fission reactions are best carried out in the absence of active nitrite groups which might alter the course of reaction. However, in view of the great complexity of possible reactions, it is evident that Aother explanations maybe more'accurate.

The actual'practlce'of the invention may perhaps be alkali is conducted at e. g. 0-50" C.v for about 1 to 30 minutes'. The proportion of water employed is not critical, but there is usually no necessity for employing more" The pH of the thanthe volume of nitration mixture. hydrolysis mixturey should be maintained between about strong alkali, or by employing a weak'base. The'total-` proportion of alkali employed should be at least stoic'hiometrically sufficient to neutralize half of the total organic nitro, nitrite and nitrate groups, as Well as anyexcess un reacted nitrogen tetroxide.

The low temperature hydrolysis mixture is then transferred via line 7, to the high temperature hydrolytic fis-- sion step 8, wherein hydrolysis under similar conditions;

of alkalinity is continued for another 2 to 90 minutes for' hydrolysis step, it may be desirable to add additional alkali via line 9 to the hydrolytic fission stage in order to( maintain the desired alkalinity. It is essential however to avoid Vhigh alkalinity, especially in the high temperature hydrolytic ssion stage, inasmuch as the soluble aciis then transferred via 4 and l0, either by limiting the instantaneous proportion of case strong alkalis are employed in the low temperature nitromethane salts formed ar'e very reactive, and prodljce ,unde'sired products. 1

Anne endet-.the hyo'mlyric fission .period therreacfion mixture is`.'tran"sfe"rred via line 11"to distillation step 12; 1

whereiny the products are separatedbypY any desired distillation systemz. The precise distillation 'procedure 'employedwillldepend'uppn th'e natureofthe `ether solvent emp1oyed, butin." any, event littleV dilculty is usually encounteredin obtainingjadequateseparation. Any re'- maining eth'er is distilled'offthrough line 13 and recycled to line 4; It is., preferred 'toemploy lower aliphatic ethers boilingmbelow.aboutA 65 rl"C., inasmuchas those materials may either be distilled frormthe reaction mixture without forming, an azeotrope,` or. in those.' cases where water azeotropes are formed; such'azeotropves contain lessthan about 4%" of water and hencemay be recycled directly tothe nitration ,step if*`the,preferred`short contacttimes are employed 'therein., Dmethyl fether and Methylmeth/yl ether for.examp`le maybe readilyrecovered without forming.,an'.azeotrope..v Methylal likewise `doesnot form an azeotrope.: Di'ethylether forms an azeotroperwith.water` which'l however contains. vonly',123%'wate1. Thermethyl-l propyl 4,ether-water, az'eotrope contains only, about 2%,V of.r water.A Any ofthese azeotropes maybe recycled, difreetly.I However, it is not'meant'to exclude the possibility ofrdehydratingth'e ether distillate prior to recycling.` This4 may `be accomplished 'by `conventional methods at-slightly.

addedexpense.

obtain nitrates.

The nitrates may then be recovered in pure form by evaporationat step 17. The inorganic.. nitrites or nitrates recovered constitute a valuable byproduct fertilizer, or they may be utilized for regenerating nitrogen tetroxide.

Many other lower molecular weight oletins may be utilized in a manner similar to that described` above. It is preferred to utilize iso-olefins, i. e. those wherein the double bond is linked to a carbon atom which contains no hydrogen atom. These preferred olens all yield ultimatelyaf nitro-alkaneandfa. ketone. The olens which"V yield laldehydes .generallvfdo `:not result :in: asghigh yields.;

of 4nitro-alliane, primarily because of Vthe greater diticulty in effecting hydrolytic ssion, andalso4 because; of com,.- plicating sidereactions brought about by the fmore1highly reactive aldehydes. Suitable oleiins,.togethenwith-then final. reaction products `are illustratedin the following,

table:

TABLE: l

Olen Reaction Products l-butene propionaldehyde,nitromethane. 2butenc acetaldehyde,nitroethaua. 2,3-dlmethylf2butene acetone, 2-nitropropane.

2-methyl2-butene 2-methy1-1-butene methylldene cyclohexane 2,4,4-trimetliyl petitorio-1 (dliso-Y buten 2.4,4-trimethyl pentenc-Z; 2,31imethyl butene-l 2-tsopropenyl benzene-.

acetone, ,nitroethane cyelohexanone, nitromethane.

methyLmeopentyl ketone, nitromethane. acetone, nltroneopentane.Y

methyl isopropyl ketone, nitro-` methane. diethyl ketone, nitromethane. methyl., isobutyl ketone, nitromethane. acetophenone, nitromethane.

Toefurthervillustme `thel novel-'features of the invention, 75?

the followingpexamples are cit ed, which should nothowever be-conside'red as limiting in scope:

Example 1.,-Ba

A: Ntraton'.-Seventy rnl.` anhydrous nitrogen tetroxide tch filtration (102 gms.) of` redistilled, wasadded to 400 ml. of-

anhydrous Vdiethyl` ether'at 20 C. A stream of oxygen was bubbled throughth'e solution untilfit became alightA brown- (originally 'dark brown indicatingthat all N203` was oxidized to N204. lsobutene at therateof 1.5 s. c.f.V per hourwas then-added, alongwith a stream ofoxygen at the rate of 0.5 s. c.f. per hour. The addition of isobutene'and'oxygen was continued until thebrown color disappeared, indicating/that the N204 was completely com sumed.- The temperature during the nitration'rangedn fromI -109 to-{14 C. The resulting nitrated product is found to'consist almost" exclusively rof-`nit`rotertbutyl nitrite,- 1,2

dinitro isobutane andenitro-tertbutyl nitrate.`

B. Hydrolysis.-The nitration `mixture from partlA -was then Aadded with stirringto--l liter of water at27" C; containing V1 mole-(81 gms.) `of-zinc'oxide.

The slurry was- C., and maintained inl that-4 range for 2 hours while continuously distilling otfproduct at reduced pressure; Forty-six Aml; of nitromethane-(89% yield,1based-on 0.5`-of original N204) was obtained; and* 44 ml.` of acetone` (54% N204).

yield basedlon 0.5 of original) This example shows that v high yieldsof` nitromethane may Vbe obtained. 1in batch-scale Voperation if fthe reactants are` anhydrous, and "eventhough there is not an-excessof N204 throughout thenitration:

Example II The procedure of Example?- rIiwas repeated except that the nitration-mixture from .partA was added dropwise to theHzOfZnOhydroly/sis mediumwhile the latter` was maintained'continuouslyi at 95 98 C. The product was removed continuously as water azeotrope at atmospheric pressure.

Fractionation of theiproduct gave 16 ml. of

nitromethane (31.5% of theoretical) and 9 ml. of 2.nitro isobutene. Most of thefNzOs theoretically convertiblefto` nitromethane'was consumed in undesired side-reactions,

apparently because fission was=not preceded temperature hydrolysis stages Example :III

with the nitrationtemperasl ture controlled at -10-0 uct was then added to a sl C. The -cold nitration pr0d urry of 100 gms. of calcium carbonate in l literof distilled water at room temperature. The resultlngfmixture was then heatedgradually over a periodofabout '25 minutesto `100 was yel1ow,and changed'to-buff at C. The cold mixture 65 C., and to orange at 90 C. The'productwas thendistilled overhead; along with'fthe ether-solvent.` acetone (77% (86% of theoretical).

Fractionation yielded 60 ml. of -oftheoreticaD and 44ml. of nitromethane This-example shows that calcium carbonate is equally` as effective-in the Yhydrolysis; st alkaline materials arefo'und to as the bpHis. not'allowed` to;

ep as is zinc oxide. Other function similarly, so long rise into the range wh'ere aci-nitro saltsare formed `or to fall intothe range where appreciable amounts' of free nitrous acid are present. For

example,- in a parallel run employing l mole of potassium bicarbonateiasythe alkali,.a 73% yield of nitromethane anda 59 %"yield:of acetone was obtained.

When Examples I and III undried ether *(14%l water), toneW yields are. substantially reduced. O `N204 1s maintained throughout are repeated, empldyingI the nitromethane audace If an` excess of while-using undried ether,

somewhat' better results are obtained, but not as goodas when dry reactants andr stoichiometric proportions of` N204' are employed.

Example` I V.Continuous ntratn A coiled tubular reactor, 2 mm. in inside diameter and 12 ft. in length was constructed and immersed in an ice bath. The outlet led through a condenser to a ask equipped with a mechanical stirrer containing the hydrolysis medium. Liquid diethyl ether was pumped into the inlet of the reactor by means of a constant rate pump. A stream of oxygen plus nitrogen was bubbled through a reservoir of liquid nitrogen tetroxide at about C., and the total gas stream was then admitted to the inlet ether line.v Liquid isobutene was metered into the inlet line at a point downstreamward from the N204-0zN2 inlet. In all cases the ice bath was maintained at 0 to C.

Run 4-a.-Anhydrous diethyl ether and redistilled N204 was employed. The ether was pumped in at the rate of about 180 mL/hr. the oxygen and nitrogen liow rates through the liquid N204 were 1.2 and 0.4 s. c. f. per hour, respectively. Isobutene was added at the rate of 1.2 s. c. f. (1.5 moles) per hour. The nitration product was continuously passed into the hydrolysis ask containing 80 gms. of zinc oxide in l liter of distilled water. The temperature of the hydrolysis flask was maintained at about 23-26 C. throughout the nitration period of one hour. During this period 67 gms. (0.73 mole) of N204 had been passed through the reactor. `The liquid residence time in the nitration reactor was about 5 sec., as determined by timing the passage of a color-indicator therethrough.

At the `end of one hour the nitration was interrupted, and the contents of the hydrolysis flask, together with ml. of undecanol to prevent foaming, were heated to boiling and the inal products distilled overhead and fractionated. Substantially all of the ether and unreacted isobutene was recovered, and 37 gms. of nitromethane (83% of theoretical) and 33 ml. of acetone (62% of theoretical) Run 4-b.-Run 4-a is repeated employing commercial N204 and the water azeotrope of diethyl ether containing about 1.3% by volume of water. The yield of nitromethane and acetone is the same as in run 4-a, within experimental error, showing that the deleterious effects of water are overcome by operating at short contact times. No appreciable decrease in yield is noted with nitration mixtures containing up to 3% by volume of water.

Run 4-c.-The procedure of run 4-11 is repeated omitting the use of oxygen. The nitrogen ow rate through the reactor was increased to 1.6 s. c. f. per hour. Again the yield of nitromethane is greater than 80% and of acetone about 65%, based on N204, showing that oxygen is not necessary at short contact times.

Run 4-d.-The procedure of run 4-a is repeated With an oxygen iiow rate of 0.6 s. c. f. per hour and a nitrogen flow rate of 0.2 s. c. f. per hour, whereby the residence time in the reactor is approximately doubled (l0 sec.). The yield of nitromethane is about 65% and of acetone about 45%, showing that the 5 sec. contact time is preferable to 10 sec.

Run 4-e.-Run 4-a is repeated, but the nitration product is passed directly into a boiling (100 C.) zinc oxide hydrolysis mixture. The nitromethane yield is about 45%.

Example V Gaseous propylene is subjected to nitration under conditions similar to those described in Example la, with the nitration temperature being maintained at 0 C. The resulting nitrated product is then poured into one liter of boiling water. Hydrolysis is continued for about 1 hour, during which time a 20% yield of nitropropylene was distilled overhead. The remaining aqueous solution is found to contain a large proportion of 2-nitro isopropanol and polymerized nitro propylene. The nitro alcohol is more resistant to hydrolytic fission than `are the nitro-tertiary alkanols.

By nitrating a stream of propylene continuously as described in Example 4-a, with a l minute liquid resi- 10 dence time, and passing water, a similar yield of total nitrated products is recovered.

v Example VI 70 ml. of commercial nitrogen tetroxide were added to 400 ml. anhydrousdiethyl ether at -20 C. Oxygen was passed through the mixture until it became light brown in color. Di-isobutylene (156 ml.) was then added at a rate of 60 drops per minute while continuing to pass oxygen through the mixture at the rate of 0.5 s. c. f. per hour. The nitration temperature was maintained about The nitration mixture was then poured into a slurry of gms. calcium carbonate in 1 liter of water and the slurry was gradually heated with stirring. Fractionation of the distillate resulted in the recovery of 20 grams of nitromethane and 49 grams of methyl neopentyl ketone.

Substantially similar results are obtained when other isooleiins are employed in the above examples. Similarly, essentially the same results are obtained when other ether type solvents are employed, with the exception that the iinaly product recovery system must be modied to accountfor the diierent boiling points.

It is contemplated that many changes may be made in the various details of the process. The true scope of the invention should therefore not be considered as limited to the above' description, but is intended to be embraced by the following claims.

I claim:

1. A method for preparing a lower nitroalkane and a lower aliphatic ketone from an addition product of nitrogen tetroxide and a lower isoolein, said addition product including both a dinitro alkane and a nitro-alkylnitrite, which comprises contacting said addition product in a irst contacting stage with an aqueous alkaline hydrolytic reagent at a temperature between about 0 and 50 C. for a period of time sufficient to hydrolyze substantially all organic nitrite groups to hydroxyl groups but insutiicient to eiect any substantial iission of carbonto-carbon bonds, then continuing said contacting in a second stage at a temperature between about 50 and C. for a period of time suicient to effect fission of substantially all nitro compounds containing the same number of carbon atoms as the original olefin, maintaining the pH in each of said hydrolytic contacting stages at between about 4 and l0, and thereafter recovering a nitroalkane and a ketone from the hydrolysis mixture.

2. A method for preparing nitromethane and acetone from an addition product of nitrogen tetroxide and isobutene, said addition product including both 1,2-dinitro isobutane and nitro-tert-butyl nitrite, which comprises contacting said addition product in a first contacting stage with an aqueous alkaline hydrolytic reagent at a temperature between about 0 and 50 C. for a period of time between about 1 and 30 minutes to thereby eiect hydrolysis of nitrite groups, then continuing said hydrolytic contacting in a second stage at a temperature between about 50 and 150 C. for a period of time between about 2 and 90 minutes to eiect fission of substantially all nitro compounds containing four carbon atoms, maintaining the pH in each of said hydrolytic contacting stages at between about 4 and 10, and thereafter recovering nitromethane and acetone.

3. A process as deiined in claim 2 wherein said hydrolytic reagent comprises water and Zinc oxide.

4. A process as defined in claim 2 wherein said hydrolytic reagent comprises water and calcium carbonate.

5. A method for preparing a lower nitroalkane and a lower aliphaticV ketone which comprises contacting a lower isooleiin with liquid nitrogen tetroxide at a temperature between about 25 and +30 C. in the presence of a solvent which is essentially a water azeotrope of an aliphatic ether boiling below about 65 C., said contacting being eected by (1) continuously admixing said etherthe nitrated product intocold diately. thereafter `passing the resultingV mixture through" an 'elongated tubular reactor maintained atatemperature between about 25 and +30 C., (3) adjusting the flow' rate of said mixture through said reactor so as to maintain.a liquid` residence time therein betweenabout 0.1 second and "21minutes to produce ,therebyan intermediate mixture of addition compounds `including a di'nitro alkane and 'anitro-alkylnitrite, contacting said intermediate mixture with an aqueous alkaline hydrolytick reagent `at a temperature suiciently high to effect lhydrolytic iission ofiI said addition compounds while maintaining the pH of 'the hydrolysis mixture at between about 4 and 10, distillingsaid ether-water azeotrope from the hydrolysis mixture andreCYClng-said azeotrope to saidV nitration contacting, step, andthereaftermecovering a nitroalkane and `a ke'toncfrom the hydrolysis .mixture 6. A metllod'for preparingy nitromethane and acetone which comprises contacting isobutene with liquid nitrogen tetroxide at a temperature between about 25 and +30 C. in the presence of a solvent which' is essentially a water azeotrope of Aanoaliphatic ether boiling below about 65 C., saidcontacting being effected by (1) continuously admixing saidether-water azeotrope, nitrogen tetroxide and isobutene, (2) immediatelythereafter passing the resultingrnixture through an elongated tubular reactorimaintained at a temperature between about 25 and ,+30" C., (3) adjusting the flow rate of said mixture through said reactor so as to. maintain a liquid residence time therein between about Oil second and 2 minutes, to` produce thereby an intermediate mixture of addition compounds including 1,2-dinitro isobutane and nitroftertbutyl nitrite, contacting,saidintermediate mixture in a first contacting stage with an aqueous alkaline hydrolytic reagent at a temperature between about 0 and.50 C.

for a period of time ,between'about 1 and 30 minutes to thereby leiiecthydrolysis of nitritegroups; continuing said hydrolytic contacting in asecondstage at a temperature betweenabout'SO" and' 150 C. for. a period oftimef between about 2 `and `9()"minutes toetfect tissionofsubstantiallyall nitro'compounds containing 4 carbon atoms;

maintaining the pHineach of'said hydrolytic'contacting' stages at betweeniaboutf4 and t 10,` distilling said etherwater azeotrope from the hydrolysisfmixture` andrecycling said azeotrope to` said nitration contacting step, and thereafter recovering nitromethaneand-'acetone from the hydrolysis mixture.

7. A process as defined in claim 6 wherein substantiallyi equal mole-ratios of'isobutene and nitrogentetroxide are` employedin said nitratiom `whereby the `nitration ,euent passed to `said hydrolyticcontactingI is. substantially free of` isobutene and nitrogen tetroxide:

8; A` process as defined Ain claim vwherein the m'ole. ratio of isobutene nitrogentetroxide employedin said nitration'step is greater than 1, whereby the nitration effluent passedto said'hydrolyticcontacting is substantial# ly free'of nitrogen tetroxide;-

References-Cited=in thefle of this patent UNITED STATES PATENTS 2,314,615 Franklin et al Mar.23,11943` 2,402,315 Crowder June.f18,. 1946 2,460,243 Scaife `et-'al lian.Y 25,. 1949 2,472,550` SmithA June 7,"1949 2,478,243; Coe etl al. Aug. 9,- 1949 oTHE-R- REFIERENCESy J.' Chemfsac. (Levyet ai): 194s, London,-pp. 52450.` 

1. A METHOD FOR PREPARING A LOWER NITROALKANE AND A LOWER ALIPHATIC KETONE FROM AN ADDITION PRODUCT OF NITROGEN TETROXIDE AND A LOWER ISOOLEFIN, SAID ADDITION PRODUCT INCLUDING BOTH A DINITRO ALKANE AND AN NITRO-ALKYLNITRITE, WHICH COMPRISES CONTACTING SAID ADDITION PRODUCT IN A FIRST CONTACTING STAGE WITH AN AQUEOUS ALKALINE HYDROLYTIC REAGENT AT A TEMPERATURE BETWEEN ABOUT 0* AND 50*C. FOR A PERIOD OF TIME SUFFICIENT TO HYDROLYZE SUBSTANTIALLY ALL ORGANIC NITRITE GROUPS TO HYDROLYZE GROUPS BUT INSUFFICIENT TO EFFECT ANY SUBSTANTIAL FISSION OF CARBONTO-CARBON BONDS, THEN CONTINUING SAID CONTACTING IN A SECOND STAGE AT A TEMPERATURE BETWEEN ABOUT 50* AND 150*C. FOR A PERIOD OF TIME SUFFICIENT TO EFFECT FISSION OF SUBSTANTIALLY ALL NITRO COMPOUNDS CONTAINING THE SAME NUMBER OF CARBON ATOMS AS THE ORGINAL OLEFIN, MAINTAINING THE PH IN EACH OF SAID HYDROLYTIC CONTACTING STAGES AT BETWEEN ABOUT 4 TO 10, AND THEREAFTER RECOVERING A NITROALKANE AND A KETONE FROM THE HYDROLYSIS MIXTURE. 